1. Field of the Invention
The present invention relates to a binocular stereo microscope to observe an eye to be operated on, and more particularly to an alignment structure of a binocular stereo microscope provided in an operation apparatus for operating on a cornea and the like to change the curvature of the cornea.
2. Description of Related Art
Conventionally, there are many kinds of binocular stereo microscopes used in the conventional operation apparatus for operating on the cornea. Regarding the alignment of such binocular stereo microscope to arrange the eye to be operated on and the laser beam transmitting optical system for transmitting the therapeutic laser beam into the eye to be operated on relatively in a proper position, the following methods have been proposed.
For example, one method is adjusting a reticule inserted into one eyepiece part of the observation optical system in the binocular stereo microscope to the illumination light image reflected by the cornea or an image of the anterior eye, while looking through the eyepiece.
Further, Japanese Laid-open Patent Application No. HEI 3(1991)-218744 proposes the apparatus which is arranged with an image detecting means at a position diverged from the optical system of a binocular stereo microscope to display the anterior eye to be operated on and the reticule or a scale and the like on a monitor, so that the alignment of the stereo microscope will be performed by putting the reticule and the like over the anterior eye on the monitor.
However, in the former method inserting a reticule into one eye of the eyepiece part of the binocular stereo microscope, both the right and left optical axis of the observation optical system in the binocular stereo microscope are inclined at an angle respectively to a line linking an apex and a curvature center of a cornea. Therefore, it is difficult to put a reticule over an image of the anterior eye precisely under the influence of the diopter of the stereo microscope and achieve focusing accuracy according to an inclination of respective optical axis of the observation optical system.
In the latter alignment method using a monitor, because of arranging an image detecting means coaxially with the optical axis linking the apex and the curvature center of cornea of the patient's eye, it is possible to prevent the positional deviation between the reticule and the image of anterior eye caused by the inclination of the optical axis. But whether the anterior eye and the reticule are placed at a proper position on a monitor depend on the observer's judgement, and the alignment condition depend on the intuition and the experience of the operator handling the binocular stereo microscope. Consequently, a good alignment can be not always obtained. Further, the operator must look at a monitor for alignment and then through an eyepiece for observing the patient's eye in turn.